1. Technical Field
The invention relates to a color printing control device, a color printing control method, and a computer readable recording medium stored with a color printing control program.
The invention is related to a color printing device, a color printing control method, and a computer readable recording medium stored with a color printing control program each having a mode for executing a printing process by saving color materials,
2. Description of Related Art
Most color printing devices accomplish full-color printing by overlaying images each produced in one of the four color materials, i.e., cyan (C), magenta (M), yellow (Y), and black (K) on a printing medium. As such, the cost of color printing tends to be more expensive than monochromatic (grayscale) printing, which is printed with black (K) color material alone, as it consumes more color materials.
For example, when the test chart defined in ISO/IEC 24712:2006 “Color test pages for measurement of office equipment consumable yield” is printed with a full-color laser beam printer, it consumes twice as much color materials (toners in this case) compared to a case of printing the same test chart in grayscale. Also, when a color patch (RGB 216-color patch) expressed as a combination of 0%, 20%, 40%, 60%, 80% or 100% of each one of three colors, i.e., red (R), green (G) and blue (B) is printed in color, it consumes approximately three times as much color materials compared to a case of printing the same color patch in grayscale.
Incidentally, it is preferable that printing cost is kept as low as possible when the purpose of printing is to proof the manuscript or to check its layout
For such needs available are color printing devices having printing modes that save printing cost by suppressing the consumption of color materials. As the means of realizing the printing modes for suppressing the color material consumptions, methods of printing color pictures are used such as (1) converting colors into grayscale; (2) reducing the color image density of each color material; (3) with a reduced total number of pixels by skipping pixels of each color material, etc.
However, in the method (1) of printing by converting color images into grayscale, color information is discarded in the conversion so that it is difficult to check the enhancement effect of characters expressed, for example, in red in order to stand out in the original manuscript, because they become weaker in density than unstressed characters in black as they are converted. Also, yellow is essentially a color with a high luminosity, so that it becomes very weak when it is converted into grayscale, and becomes unidentifiable from the printing ground (white). In the method (2) of printing with a reduced color image density for each color material, it is necessary to reduce the image color density to approximately 50% in order to print the abovementioned RGB 216 color patch with the same amount of color material consumption equivalent to that of grayscale printing. However, since gradation reproduction is achieved with dither screens in most color printing devices, reduction of density means constituting printing images with smaller dither dots, which worsens especially the legibility of small font characters. The method (3) of skipping pixels of each color material causes printed images to blur, again worsening the legibility of small font characters. Moreover, any attempt of maintaining or improving legibility using these methods results in spoiling the effort of reducing color material consumption.
On the other hand, technology is proposed for saving color materials consumed in printing by modifying the chroma or luminosity of pixels so as to specify a gray pixel to be printed by a combination of color inks and to print the particular pixel with a black ink alone. See Unexamined Japanese Patent Publication No. 2005-512199.
However, the technology described in the abovementioned patent document is a color material reduction process to reduce color materials by intervening with printing data on a host computer or a communication route between a host computer and a color printing device. Incidentally, PostScript® is capable of describing an object defined in various color spaces with a single set of printing data. Therefore, the color material reduction process in the technology described in patent document 1 has to be able to handle various printing data formats and color space definitions of various PDL (Page Description Languages), which creates a problem that it requires a large amount of date resources to be able to respond individually. Moreover, a color printing device has also been proposed recently, which is equipped with an interface so as to be able to print by reading data stored in a memory device (memory direct printing function). A problem of the technology described in the abovementioned patent document is that it cannot handle printing that completes within a color printing device without dealing with a host computer.